1. Field of the Invention
The present invention is related to a semiconductor device and in particular, a semiconductor device having a super junction which includes a columnar region which extends in the thickness direction of a substrate.
2. Description of the Related Art
A semiconductor device having a super junction structure is conventionally known. In patent document 1 (Japan Laid Open Patent 2006-5275), a semiconductor device is disclosed having a super junction structure arranged with a cell region formed with a plurality of semiconductor elements and a periphery region for resistance improvement. In a cell region of this semiconductor device, a plurality of first p type columnar regions and a plurality of first n type columnar regions are alternately formed. In the periphery region, a plurality of second p type columnar regions and a plurality of second n type columnar regions are alternately formed. Furthermore, in the periphery region, a third p type columnar region and an n type high resistance layer are formed on an upper layer of the above stated second p type columnar regions and the second n type columnar regions.
Here, the depth of the first p type and the first n type columnar region is deeper than the depth of the second p type and second n type columnar region. In addition, the width of the second p type columnar region is different to the width of the third columnar region.
In the semiconductor device described in patent document 1, it is possible to reduce the variation in the amount of impurities in each columnar region by using a third p type columnar region. In this way, it is possible to make the ratio (charge ratio) between a charge of a p type columnar region and a charge of an n type columnar region constant, and it is possible to improve the resistance of the semiconductor device.
However, in the technology disclosed in patent document 1, there is the problem that the manufacturing process becomes complex because the depth and width of columnar regions are different. In particular, when the depth of columnar regions is different, it is difficult to make the amount of purities in each columnar region equal and it is very difficult to adjust the amount of implanted ions.